---
title: Database Adapters
description: Comprehensive guide to the database adapter system in c15t Backend, covering available adapters, query interface, and performance considerations.
lastModified: 2025-04-15
deprecated: true
deprecatedReason: "@c15t/backend v1 did not deliver the flexibility we wanted and fell short of our standards. It is now deprecated as we work on a full rewrite, with v2 entering canary soon. This does not affect consent.io deployments, which remain stable."
---

The c15t Backend package provides a flexible database adapter system that allows you to use different database backends while maintaining a consistent interface.

## Overview

Database adapters provide a standardized way to interact with different database systems. Each adapter implements the `DatabaseAdapter` interface:

```typescript
interface DatabaseAdapter {
  create: <T extends Record<string, unknown>>(table: string, data: T) => Promise<T>;
  find: <T extends Record<string, unknown>>(table: string, query: Query) => Promise<T[]>;
  update: <T extends Record<string, unknown>>(table: string, query: Query, data: Partial<T>) => Promise<T>;
  delete: (table: string, query: Query) => Promise<void>;
}
```

## Available Adapters

### Memory Adapter

The memory adapter is perfect for development and testing. It stores data in memory and is reset when the application restarts.

```typescript
import { memoryAdapter } from '@c15t/backend/db/adapters/memory';

const instance = c15tInstance({
  baseURL: 'http://localhost:3000',
  database: memoryAdapter({}),
});
```

#### Features

- In-memory storage
- No persistence
- Fast for development
- Automatic cleanup

### Kysely Adapter

The Kysely adapter provides type-safe SQL query building with support for multiple databases.

```typescript
import { kyselyAdapter } from '@c15t/backend/db/adapters/kysely';

const instance = c15tInstance({
  baseURL: 'http://localhost:3000',
  database: kyselyAdapter({
    dialect: 'postgres',
    connection: {
      host: 'localhost',
      port: 5432,
      database: 'c15t',
      user: 'postgres',
      password: 'password',
    },
  }),
});
```

#### Supported Databases

- PostgreSQL
- MySQL
- SQLite
- Microsoft SQL Server

#### Features

- Type-safe queries
- Query building
- Transaction support
- Connection pooling

### Prisma Adapter

The Prisma adapter integrates with Prisma ORM for type-safe database access.

```typescript
import { prismaAdapter } from '@c15t/backend/db/adapters/prisma';
import { PrismaClient } from '@prisma/client';

const prisma = new PrismaClient();

const instance = c15tInstance({
  baseURL: 'http://localhost:3000',
  database: prismaAdapter({ client: prisma }),
});
```

#### Features

- Prisma ORM integration
- Type safety
- Schema management
- Migration support

### Drizzle Adapter

The Drizzle adapter provides integration with Drizzle ORM.

```typescript
import { drizzleAdapter } from '@c15t/backend/db/adapters/drizzle';
import { drizzle } from 'drizzle-orm/node-postgres';
import { Pool } from 'pg';

const pool = new Pool({
  connectionString: 'postgres://user:password@localhost:5432/c15t',
});

const db = drizzle(pool);

const instance = c15tInstance({
	baseURL: 'http://localhost:3000',
	database: drizzleAdapter(
		db as unknown as { [p: string]: unknown },
		{
			provider: 'pg',
		},
	),
});
```

#### Features

- Drizzle ORM integration
- Type safety
- Schema management
- Query building

## Creating Custom Adapters

You can create custom adapters by implementing the `DatabaseAdapter` interface:

```typescript
class CustomAdapter implements DatabaseAdapter {
  async create<T extends Record<string, unknown>>(
    table: string,
    data: T
  ): Promise<T> {
    // Implementation
  }

  async find<T extends Record<string, unknown>>(
    table: string,
    query: Query
  ): Promise<T[]> {
    // Implementation
  }

  async update<T extends Record<string, unknown>>(
    table: string,
    query: Query,
    data: Partial<T>
  ): Promise<T> {
    // Implementation
  }

  async delete(table: string, query: Query): Promise<void> {
    // Implementation
  }
}
```

## Query Interface

The query interface is consistent across all adapters:

```typescript
interface Query {
  where?: Record<string, unknown>;
  orderBy?: Record<string, 'asc' | 'desc'>;
  limit?: number;
  offset?: number;
  include?: Record<string, boolean>;
}
```

### Example Queries

```typescript
// Find with conditions
const users = await adapter.find('users', {
  where: { active: true },
  orderBy: { createdAt: 'desc' },
  limit: 10,
});

// Update with conditions
const updated = await adapter.update(
  'users',
  { where: { id: '123' } },
  { name: 'New Name' }
);

// Delete with conditions
await adapter.delete('users', { where: { id: '123' } });
```

## Transaction Support

Some adapters support transactions:

```typescript
// Kysely adapter example
const result = await adapter.transaction(async (trx) => {
  await trx.create('users', { name: 'John' });
  await trx.create('profiles', { userId: '123' });
  return 'success';
});
```

## Error Handling

Adapters handle errors consistently:

```typescript
try {
  const result = await adapter.create('users', data);
} catch (error) {
  if (error instanceof DatabaseError) {
    // Handle database-specific errors
  } else {
    // Handle other errors
  }
}
```

## Best Practices

1. **Connection Management**
   ```typescript
   // Create a single connection pool
   const pool = new Pool({
     max: 20, // Maximum number of connections
     idleTimeoutMillis: 30000,
   });
   ```

2. **Error Handling**
   ```typescript
   const adapter = kyselyAdapter({
     dialect: 'postgres',
     connection: {
       // ... connection config
     },
     onError: (error) => {
       // Log errors
       console.error('Database error:', error);
     },
   });
   ```

3. **Query Optimization**
   ```typescript
   // Use indexes
   await adapter.create('users', {
     email: 'user@example.com',
     // Add indexed fields
   });

   // Use appropriate query conditions
   const users = await adapter.find('users', {
     where: { email: { $like: '%@example.com' } },
     limit: 100,
   });
   ```

## Migration Support

Adapters that support migrations provide methods for managing database schema:

```typescript
// Kysely adapter example
const migrations = await adapter.getMigrations();
await adapter.runMigrations(migrations);
```

## Performance Considerations

1. **Connection Pooling**
   - Configure appropriate pool size
   - Monitor connection usage
   - Handle connection errors

2. **Query Optimization**
   - Use indexes
   - Limit result sets
   - Optimize join operations

3. **Caching**
   - Implement caching where appropriate
   - Use appropriate cache invalidation
   - Monitor cache hit rates

## Security

1. **Input Validation**
   ```typescript
   // Validate input before database operations
   const validatedData = validateUserInput(data);
   await adapter.create('users', validatedData);
   ```

2. **SQL Injection Prevention**
   - Use parameterized queries
   - Validate input
   - Escape special characters

3. **Access Control**
   - Implement row-level security
   - Use appropriate database roles
   - Monitor access patterns

## Monitoring and Debugging

1. **Query Logging**
   ```typescript
   const adapter = kyselyAdapter({
     dialect: 'postgres',
     connection: {
       // ... connection config
     },
     debug: true, // Enable query logging
   });
   ```

2. **Performance Monitoring**
   - Track query execution time
   - Monitor connection pool usage
   - Log slow queries

3. **Error Tracking**
   - Log database errors
   - Track failed queries
   - Monitor connection issues
